#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <algorithm>
using namespace std;

struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};

class Solution
{
public:
    int minDepth(TreeNode *root)
    {
        if (root == nullptr)
            return 0;

        if (root->left == nullptr && root->right != nullptr)
        {
            return 1 + minDepth(root->left);
        }
        if (root->left != nullptr && root->right == nullptr)
        {
            return 1 + minDepth(root->right);
        }
        return 1 + min(minDepth(root->left), minDepth(root->right));
    }
};